Variable thickness golf club head and method of manufacturing the same

ABSTRACT

A method of forming a crown of a golf club head including casting the crown of the golf club head, the crown including an internal surface adjacent a hollow interior of the golf club head, and an external surface opposite the internal surface, the crown including a first region and a second region adjacent the first region, the first region including a recess formed in the internal surface, the first region including a sacrificial protrusion on the external surface extending outwards beyond the second region; applying a mask to the external surface of the second region; exposing the crown of the golf club head to an etching chemical, wherein the etching chemical removes the sacrificial protrusion from the external surface of the crown; removing the etching chemical from the crown of the golf club head; and removing the mask from the second region.

RELATED APPLICATIONS

The current application is a continuation-in-part (CIP) of U.S. patentapplication Ser. No. 14/330,165, filed on Jul. 14, 2014, currentlypending, which is a continuation-in-part (CIP) of U.S. patentapplication Ser. No. 13/467,102, filed on May 9, 2012, abandoned, thedisclosure of which are incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a variable thickness golf club head anda method of manufacturing the same. More specifically, the presentinvention relates to systems, devices, and methods related toconstructing portions of a golf club head incorporating variablethickness.

BACKGROUND OF THE INVENTION

Ever since the metalwood golf club burst onto the scene to replace thetraditional persimmon wood, golf club designers have constantly soughtto find ways to improve upon this groundbreaking design.

U.S. Pat. No. 5,474,296 to Schmidt et al. illustrate one of the earlierattempts to improve upon the design opportunity created by a hollowmetalwood golf club by disclosing a golf club with a variable faceplatethickness. One way a variable faceplate thickness improves theperformance of a metalwood club is by reducing the amount of weight atlow stress areas of the striking faceplate to create more discretionaryweight that can be placed at alternative locations in the golf club headto improve the performance of the golf club head. In addition to theabove benefit, the incorporation of variable faceplate thickness canalso improve upon the performance of the golf club head by adjusting thecoefficient of restitution of the striking face.

U.S. Pat. No. 6,863,626 to Evans et al. illustrates this secondarybenefit of adjusting the coefficient of restitution of a golf club bydisclosing a golf club having a striking plate with regions of varyingthickness. More specifically, U.S. Pat. No. 6,863,626 identifies thisbenefit by indicating that striking plate having regions of varyingthickness allows for more compliance during impact with a golf ball,which in turn, could generate more ballspeed.

U.S. Pat. No. 7,137,907 to Gibbs et al. illustrates the ability tofurther improve upon the design of a striking face having a variableface thickness for a purpose that is different from saving weight andimproving coefficient of restitution. More specifically, U.S. Pat. No.7,137,907 illustrates a way to expand upon the “sweet spot” of a golfclub head in order to conform to the rules of golf that puts a cap onthe maximum coefficient of restitution allowed by a golf club. U.S. Pat.No. 7,137,907 does this by disclosing a golf club face or face insertwherein the face has an interior surface with a first thickness sectionand a second thickness region. The first thickness section preferablyhas a thickness that is at least 0.025 inch greater than the thicknessof the second thickness region. The face or face insert with variablethickness allows for a face or face insert with less mass in a golf clubhead that conforms to the United States Golf Association regulations.

With the incorporation of variable face thickness into hollow metalwoodtype golf club heads, various methodologies of manufacturing have beendeveloped to create this complicated geometry. U.S. Pat. No. 6,354,962to Galloway et al. illustrates one methodology to create a strikingwherein the face member is composed of a single piece of metal, and ispreferably composed of a forged metal material, more preferably a forgedtitanium material. However, due to the need for precise geometry, thevariable face geometry created by this conventional forging process mayoften exhibit waviness which will often need to be machined to the exactprecise geometry. U.S. Pat. No. 7,338,388 to Schweigert et al. discussesthis machining process by utilizing a ball end mill revolving about anaxis generally normal to the inner surface of the face plate at aninitial location on a circumferential intersection between the outeredge of the central thickened region and a transition region. The innersurface of the face plate is machined by moving the revolving ball endmill in a radial direction outwardly toward and through the transitionregion and the peripheral region to machine the inner surface of theface plate creating a tool channel having a width as the ball end milltraverses the transition region and thereby vary the thickness of theface plate in the tool path.

Although the machining process described above may be capable ofcreating a very precise geometry, the resulting striking face couldstill be flawed due to some inherent machining side effects. Undesirableside effects such as the existence of machine marks, circular cuttingpatterns, discontinuity of machine lines, starting and stopping marks,and/or machine chatters could all adversely affect the striking face.

U.S. Pat. No. 6,966,848 to Kusumoto attempts to address this issue oftrying to create an improved striking face of a golf club head bydisclosing a methodology wherein the stamped out face material is placedin a die assembly, wherein the face material is being thinned by causingthe face material to plastically deform via pressing an upper dietogether with the lower die. Although this particular type ofconventional forging methodology eliminates the adverse side effects ofmachining above described, it suffers from an entirely different set ofadverse side effect. More specifically, the conventional forging of aface insert suffers from lack of material consistency and materialtransformation that results when a material is melted and plasticallydeformed resulting in grain growth and oxidation; both of which canlower the material strength of a material.

In addition to the above flaws in the current manufacturing techniques,these flaws of the current techniques become even more apparent when adesigner seeks to further advance the performance of a striking face byimplementing non-symmetrical geometries that would either requireextensive machining, or extreme sacrifice in material property dependingon the solution selected.

Hence, as it can be seen from above, despite all the attempts inaddressing the consistency and accuracy issue in creating the variablethickness geometry in a golf club head, the current art falls short inproviding a methodology that can address the issues above. Ultimately,it can be seen from above that there is a need in the art for amethodology of creating portions of a golf club head with variablethickness without relying on conventional property changing forgingtechniques or simple machining techniques to ensure more precision andconsistency for basic symmetrical geometries and even extremeasymmetrical geometries.

BRIEF SUMMARY OF THE INVENTION

One non-limiting embodiment of the present technology includes a methodof forming a crown of a golf club head, including: casting the crown ofthe golf club head, the crown of the golf club head including aninternal surface adjacent a hollow interior of the golf club head, andan external surface opposite the internal surface, the crown of the golfclub head including a first region and a second region adjacent thefirst region, the second region substantially surrounding the firstregion, the first region including a recess formed in the internalsurface, the first region including a sacrificial protrusion on theexternal surface extending outwards beyond the second region, whereinthe first region of has an as-cast thickness T₁, and thickness T₁ isgreater than or equal to 0.48 mm; applying a mask to the externalsurface of the second region; exposing the crown of the golf club headto an etching chemical, wherein the etching chemical removes thesacrificial protrusion from the external surface of the crown; removingthe etching chemical from the crown of the golf club head; and removingthe mask from the second region.

One non-limiting embodiment of the present technology includes a methodof forming a portion of a golf club head, including: casting the portionof the golf club head, the portion of the golf club head including aninternal surface adjacent a hollow interior of the golf club head, andan external surface opposite the internal surface, the portion of thegolf club head including a first region and a second region adjacent thefirst region, the first region including a recess formed in the internalsurface, the first region including a sacrificial protrusion on theexternal surface extending outwards beyond the second region; applying amask to the external surface of the second region; exposing the portionof the golf club head to an etching chemical; removing the etchingchemical from the portion of the golf club head; and removing the maskfrom the second region.

An additional non-limiting embodiment of the present technology includespolishing the external surface of the portion of the golf club head.

In an additional non-limiting embodiment of the present technology thefirst region of has an as-cast thickness T₁, and thickness T₁ is greaterthan or equal to 0.48 mm.

In an additional non-limiting embodiment of the present technology thethickness T₁ of the first region, after exposing the portion of the golfclub head to an etching chemical, is reduced to less than or equal to0.45 mm.

In an additional non-limiting embodiment of the present technology thethickness T₁ of the first region, after exposing the portion of the golfclub head to an etching chemical, is reduced to less than or equal to0.35 mm.

In an additional non-limiting embodiment of the present technology thethickness T₁ of the first region, after exposing the portion of the golfclub head to an etching chemical, is reduced to less than or equal to0.25 mm.

In an additional non-limiting embodiment of the present technologyexposing the portion of the golf club head to an etching chemicalremoves the sacrificial protrusion from the first region.

In an additional non-limiting embodiment of the present technologyexposing the portion of the golf club head to an etching chemical iscompleted when the external surface is substantially flush at theintersection of the first region and the second region.

In an additional non-limiting embodiment of the present technology thesecond region substantially surrounds the first region.

In an additional non-limiting embodiment of the present technology thesecond region has a thickness T₂, and wherein the recess has a depthD_(r), and wherein D_(r) is greater than or equal to T₂/2.

One non-limiting embodiment of the present technology includes a methodof forming a crown of a golf club head, including: casting the crown ofthe golf club head, the crown of the golf club head including aninternal surface adjacent a hollow interior of the golf club head, andan external surface opposite the internal surface, the crown of the golfclub head including first region and a second region adjacent the firstregion, the first region including a recess formed in the internalsurface, the first region including a sacrificial protrusion on theexternal surface extending outwards beyond the second region; applying amask to the external surface of the second region; exposing the crown ofthe golf club head to an etching chemical, wherein the etching chemicalremoves the sacrificial protrusion from the external surface of thecrown; removing the etching chemical from the crown of the golf clubhead; and removing the mask from the second region.

An additional non-limiting embodiment of the present technology includesincluding polishing the external surface of the crown of the golf clubhead.

In an additional non-limiting embodiment of the present technology thefirst region of has an as-cast thickness T₁, and thickness T₁ is greaterthan or equal to 0.48 mm.

In an additional non-limiting embodiment of the present technology thethickness T₁ of the first region, after exposing the crown of the golfclub head to an etching chemical, is reduced to less than or equal to0.45 mm.

In an additional non-limiting embodiment of the present technology thethickness T₁ of the first region after exposing the crown of the golfclub head to an etching chemical is reduced to less than or equal to0.35 mm.

In an additional non-limiting embodiment of the present technology thethickness T₁ of the first region after exposing the crown of the golfclub head to an etching chemical is reduced to less than or equal to0.25 mm.

In an additional non-limiting embodiment of the present technologyexposing the crown of the golf club head to an etching chemical iscompleted when the external surface is substantially flush at theintersection of the first region and the second region.

In an additional non-limiting embodiment of the present technology thesecond region substantially surrounds the first region.

In an additional non-limiting embodiment of the present technology thesecond region has a thickness T₂, and wherein the recess has a depthD_(r), and wherein D_(r) is greater than or equal to T₂/2.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of the invention as illustratedin the accompanying drawings. The accompanying drawings, which areincorporated herein and form a part of the specification, further serveto explain the principles of the invention and to enable a personskilled in the pertinent art to make and use the invention.

FIG. 1 shows a perspective view of a golf club head that isdisassembled.

FIG. 2 shows an internal rear view of a face insert.

FIG. 3 shows a cross-sectional view of a face insert.

FIG. 4a shows a side view of one of the steps used to create a faceinsert.

FIG. 4b shows a side view of one of the steps used to create a faceinsert.

FIG. 4c shows a side view of one of the steps used to create a faceinsert.

FIG. 5a shows a side view of one of the steps used to create a faceinsert.

FIG. 5b shows a side view of one of the steps used to create a faceinsert.

FIG. 5c shows a side view of one of the steps used to create a faceinsert.

FIG. 6a shows a cross-sectional view of a face insert.

FIG. 6b shows a cross-sectional view of a face insert.

FIG. 7 shows a perspective view of one embodiment a golf club headincluding a striking face, a crown, a sole, and a hosel.

FIG. 8 shows a front elevation view of the golf club head of FIG. 7.

FIG. 9 shows a top view of the external surface of one embodiment of acrown of a golf club head.

FIG. 10 shows a bottom view of the internal surface of the crown of FIG.9.

FIG. 11 shows a cross-sectional view of the crown of FIG. 9 taken acrosscross-sectional line C-C′ as shown in FIGS. 9 and 10.

FIG. 12 shows one embodiment of a crown of a golf club head includingheel toe ribs.

FIG. 13 shows one embodiment of a crown of a golf club head including acriss-cross rib pattern.

FIG. 14A shows a cross sectional view of the first step of the stampedforging process wherein the crown is placed between a top punch and abottom cavity configured to deform the crown.

FIG. 14B shows a cross sectional view of the next step of the stampedforging process wherein the top punch compresses towards the bottomcavity to alter the shape and geometry of the crown.

FIG. 14C shows the next step of the stamped forging process wherein thetop punch is retracted away from the bottom cavity and off of the crown.

FIG. 15A shows a cutter about to remove excess material from the crownand the cutting line.

FIG. 15B shows an intermediary stage of the cutting process wherein thecutter begins to remove excess material from the crown along the cuttingline.

FIG. 15C shows the crown wherein the excess material has been removed bythe cutter.

FIG. 16A shows the crown positioned between an external die and aninternal die.

FIG. 16B shows the crown after being bent to the desired curvature bythe internal die and external die.

FIG. 17A shows a cross sectional view of a deformed crown between acurved top punch and a curved bottom cavity.

FIG. 17B shows a cross sectional view of the crown being machined by thecutter.

FIG. 17C shows a cross sectional view of the crown after being machinedby the cutter.

FIG. 18 illustrates a perspective view of a golf club head 1000including a striking face 1100, a crown 1200, a sole 1300, and a hosel1400.

FIG. 19 illustrates a perspective view of the golf club head 1000 ofFIG. 18, including a thin region 1230 located in the crown 1200.

FIG. 20 illustrates a cross-sectional view of the crown 1200 of FIG. 19.

FIG. 21A illustrates a cross-sectional view of the crown after casting.

FIG. 21B illustrates a cross-sectional view of the crown after masking.

FIG. 21C illustrates a cross-sectional view of the crown during etching.

FIG. 21D illustrates a cross-sectional view of the crown after removingthe masking.

FIG. 22 illustrates the method of creating variable thickness geometriesin golf club heads.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description describes the best currentlycontemplated modes of carrying out the invention. The description is notto be taken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the invention, since the scope ofthe invention is best defined by the appended claims.

Various inventive features are described below and each can be usedindependently of one another or in combination with other features.However, any single inventive feature may not address any or all of theproblems discussed above or may only address one of the problemsdiscussed above. Further, one or more of the problems discussed abovemay not be fully addressed by any of the features described below.

FIG. 1 of the accompanying drawings shows a perspective view of a golfclub head 100 wherein a body portion 102 and a face insert 104 aredisassembled to show the variable face thickness at a rear portion ofthe face insert 104. It should be noted in FIG. 1 the golf club head hasthe face insert 104 forming the striking face portion of the golf clubhead 100 as one of the exemplary embodiments. However, a face insert 104type geometry is not the only way to form the striking face portion, infact numerous other geometries can be used to form the striking faceportion such as a C shaped face cup, a L shaped face cup, a T shapedface cup, or any other suitable geometry all without departing from thescope and content of the present invention.

FIG. 2 of the accompanying drawings shows a more detailed enlargedperspective view of a face insert 204 in accordance with an exemplaryembodiment of the present invention. More specifically, the internalback view of the face insert 204 allows the face center 210, centralregion 212, transition region 214, and the perimeter region 216 to allbe easily shown. In addition to showing the various regions, FIG. 2 ofthe accompanying drawings shows a cross-sectional line A-A′ horizontallydividing the face insert 204 to illustrate the relative thicknesses ofthe various regions in FIG. 3. This cross-sectional line A-A′ may alsobe known as the horizontal dividing line, spanning horizontally throughthe heel and toe portion of said face insert passing through a facecenter 210. FIG. 2 also shows a vertical dividing line B-B′, that spansvertically through the crown and sole portion of said face insertpassing through a face center 210.

FIG. 3 of the accompanying drawings shows a cross-sectional view of theface insert 304 taken across cross-sectional line A-A′ as shown in FIG.2. It should be noted that FIG. 3 of the present invention shows acentral region 312 having a first thickness d1, a first transitionregion 314 having a second thickness d2, a first perimeter region 316having a third thickness d3, a second transition region 313 having afourth thickness d4, and a second perimeter region 315 having a fifththickness d5. In one exemplary embodiment, wherein the geometry of thevariable face thickness is symmetrical, the thickness of the first andsecond transition regions 313 and 314 are the same and the thickness ofthe first and second perimeter region 315 and 316 are the same. Itshould be noted that due to the fact that the transition regions 313 and314 are constantly transitioning in thickness from the central region312 to the perimeter regions 315 and 316, the thickness of thetransition regions 313 and 314 are measured at the center of thetransition regions 313 and 314. In some instances it is preferred tohave symmetry in the variable face thickness geometry, as it makes forfairly simple and straight forward machining. However, the symmetricalgeometry may not truly optimize the weight and performancecharacteristics of a striking face, and has generally stemmed from themachining problems that can come with asymmetrical geometries.

Hence, in accordance with an alternative and preferred embodiment of thepresent invention, the face insert 304 may have an asymmetricalgeometry. More specifically, the first transition region 314 may have asecond thickness d2 that is different from the fourth thickness d4 ofthe second transition region 313, and the first perimeter region 316 mayhave a third thickness d3 that is different from the fifth thickness d5of the second perimeter region 315. Removing the restriction ofsymmetrical variable face thickness geometry removes unnecessary designrestrictions to allow a golf club designer to truly optimize the facedesign. In fact, the preference for symmetrical face geometries in aface insert has always been driven by manufacturing preferences. In oneexemplary embodiment, a golf club designer could further thin outdifferent regions of the striking face that is not subjected to thehighest level of stress, creating more discretionary mass to be moved todifferent regions of the golf club head itself.

In this exemplary embodiment, thickness d1 of the central region 312 maygenerally be greater than about 3.0 mm, more preferably greater thanabout 3.30 mm, and most preferably greater than about 3.60 mm. Thicknessd2 and d4 of the transition regions 314 and 313 respectively maygenerally decrease from about 3.60 mm to about 2.7 mm, more preferablyfrom about 3.60 mm to about 2.65 mm, and most preferably from about 3.60mm to about 2.60 mm. Finally, thickness d3 and d5 of perimeter regions316 and 315 respectively may generally also be decreasing from about2.70 mm to about 2.55 mm, more preferably from about 2.65 mm to about2.50 mm, and most preferably from about 2.60 mm to about 2.45 mm.

Based on the above, it can be seen that a new methodology needs to becreated to effectively create this constantly changing face thicknesswithout the need to machine complicated geometry that is asymmetrical.The current invention, in order to achieve this goal has created aninnovative machining process detailed in FIGS. 4a, 4b, 4c, 5a, 5b, and5c shown in the later figures.

FIG. 4a through FIG. 4c illustrates graphical depiction of the newinnovative face insert forming technique associated with an exemplaryembodiment of the present invention called “stamped forging”. Althoughthis new innovative forming technique may have some similarities to theconventional forging process, it is completely different. In fact, theconventional forging process involves deformation of the face insert 404pre-form material to create the material flow into a cavity. Thismelting of the material is undesirable when used to form the strikingface portion of the golf club head, as the melting of the material,combined with the phase transformation of the material, could result ingrain growth and oxidation of the titanium material, both of whichdiminishes the material strength of titanium.

The current process is completely different from the conventionalforging process because it involves the elements of stamping as well asforging, and can be more accurately described as “stamped forging” or“embossed forging”. During this “stamped forging” or “embossed forging”process the face-insert 404 pre-form does not experience any phasetransformation, but is merely warmed to a malleable temperature to allowdeformation without the actual melting of the face insert 404 pre-form.

More specifically, in FIG. 4a , a side view of the first step in thecurrent forming technique is shown. In FIG. 4a , the various componentsused for the formation of the face insert 404 such as the top punch 421and bottom cavity 422 are shown in more detail. More specifically, as itcan be seen from FIG. 4a , the top punch 421 has a protrusion 424created in roughly the shape of the desired variable face thicknessgeometry; while the bottom cavity 422 has a corresponding depression 426that also roughly corresponds to the shape of the desired variable facethickness geometry. Although not shown in extreme detail, FIG. 4a showsthat the bottom cavity 422 could be non-linear along the perimeter edges427 to create a constantly variable thickness across the entireperimeter surface of the face insert 404 pre-form.

FIG. 4b shows the next step of the current inventive stamped forgingmethodology wherein the top punch 421 compresses against the bottomcavity 422 to alter the shape and geometry of the face insert 404.Although the current inventive methodology does not involve the meltingof the material used to create the face insert 404, the face insert 404is generally heated up to about 830° C. for about 300 seconds on aconveyor belt to increase the malleability of the face insert 404 toallow for the deformation. In this current exemplary embodiment of theinvention the top punch 421 generally applies about 100 MPa of pressureonto the face insert 404 for about 2 seconds to create the desiredgeometry.

FIG. 4c shows the next step of the current inventive stamped forgingmethodology wherein the shape of the variable face thickness geometrybegins to take place when the top punch 421 is removed from the bottomcavity 422. It should be noted here that in this current exemplaryembodiment of the present invention, the side of the face insert 404that faces the top punch 421 will eventually form the external surfaceof the face insert 404 as it gets assembled in the golf club head, whilethe side of the face insert 404 that contacts the bottom cavity 422 willeventually form the internal surface of the face insert 404 as it getsassembled in the golf club head. This type of methodology ensures that aprecise geometry could be achieved on the internal side of the faceinsert 404 without the need for excessive machining, even if anon-symmetrical organic shape is desired to maximize the performance ofthe face insert 404.

Although the steps described above in FIGS. 4a through 4c may besufficient to create the desired geometry in some circumstances,additional steps similar to the ones described above may be repeated toachieve more precise and complicated geometries. In the alternativeembodiments wherein multiple stamped forging steps are required, theprocess could be repeated for rough and fine stamped forging withoutdeparting from the scope and content of the present invention. In fact,the steps described could be repeated three time, four times, or anynumber of times necessary to achieve the desired geometry all withoutdeparting from the scope and content of the present invention. In caseswherein multiple stamped forging steps are needed, the shape andgeometry of the top punch 421 and the bottom cavity 422 may even beslightly different from one another, with each finer mold having acloser resemblance to the final finished geometry.

Once the geometry of the internal surface of the face insert 404 isformed via the above prescribed methodology, the external surface of theface insert 404 can be machined off a flat geometry, which is asignificant improvement than the conventional methodology of actuallymachining in the complicated geometry on the rear internal surface ofthe face insert 404. FIGS. 5a through 5c illustrate the final stepsinvolved in machining off the excess material in this the current faceinsert 504 stamped forging methodology.

FIGS. 5a-5c show side views of a face insert 504 together with thebottom cavity 522 after the top punch (not shown) has created thedesired geometry by deforming the shape of the face insert 504 in theprevious steps. In these final steps, the excess material of the faceinsert 504 is removed via a cutter 530. The excess material, as shown inthis current exemplary embodiment of the present invention, maygenerally be defined as any material that is above the cutting line 531shown in FIG. 5a . This cutting line 531 is generally defined by theflat surface that significantly aligns with the bottom of the rearindentation 528 of the formed face insert 504. In fact, in mostexemplary embodiments, the cutting line 531 may actually be placedslightly below the bottom of the rear indentation 528 of the formed faceinsert 504 to allow for a precise finish of the face insert 504.

The position of this cutting line 531 can be important, as it determinesthe relative thickness of the face insert 504. Hence, in order to moreaccurately define this cutting line 531, distance d6 and d7 areidentified in FIG. 5a . Here, in this current exemplary embodimentdistance d6 signifies the distance of the final thickness of theperimeter relative to the perimeter surface of the bottom cavity 522.This distance d6 may generally vary from about 2.2 mm to about 2.6 mm,more preferably from about 2.3 mm to about 2.6 mm, and most preferablyfrom about 2.4 mm to about 2.6 mm. However, as it has already beendiscussed before the perimeter region of the face insert 504 could verywell have a variable thickness, thus making it difficult to determinethe thickness of d6; as the thickness d6 would be a function of theperimeter of the face insert 504. Thus, in order to properly index thecutter 530 to remove the correct amount of material from the frontalsurface of the striking face 504, an additional thickness d7 isidentified; measuring the distance from the bottom of the depression 526of the bottom cavity 522 to the cutting line 531 from which the removalof material is indexed. Distance d7, as it is shown in this currentexemplary embodiment of the present invention, may generally be betweenabout 3.5 mm to about 3.8 mm, more preferably between about 3.6 mm toabout 3.7 mm, and most preferably about 3.65 mm.

The cutter 530 shown in this current exemplary embodiment of the presentinvention may generally be a fly cutter type cutter to ensure a smoothsurface that will eventually form the frontal surface of a golf clubhead, however, numerous other types of cutters may be used withoutdeparting from the scope and content of the present invention. Morespecifically, alternative cutters 530 may include an end mill clutter, aball nose cutter, a side and face cutter, a woodruff cutter, a shellmill cutter, or any type of milling cutter all without departing fromthe scope and content of the present invention. In fact, the finishedsurface could even potentially be achieved by any alternative finishingtechniques that could create a flat surface all without departing fromthe scope and content of the present invention.

FIG. 5b shows an intermediary stage of the cutting process wherein thecutter 530 begins to remove excess material from the formed face insert504 along cutting line 531. Finally, FIG. 5c shows the finished productof a face insert 504 in accordance with an exemplary embodiment of thepresent invention wherein the excess material has been removed by thecutter 530. The finished face insert 504 can then be bent to therequired curvature to match the bulge and roll of a golf club head andinstalled to complete the golf club head. As it can be seen from above,the innovative forming and finishing method is a major improvement insimplifying the machining process involved to a simple one pass finish,especially when compared to the conventional method of machining theactual variable thickness geometry. This advantage of not having tomachine the actual geometry becomes even more apparent when the variablegeometry implemented involves non-symmetrical shapes, as those types ofgeometries become extremely difficult to machine using conventionalmachining methods.

FIGS. 6a and 6b show alternative embodiments of the present inventionwherein the frontal indentation 628 of the striking face insert 622 arepreserved and not machined off. In these embodiments, the frontalindentation 628 could be filled with a secondary material that isdifferent from the material used to create the face insert 622 to createa striking face insert 622 that incorporates multiple materials. Thefiller 630 in this current exemplary embodiment could be made out ofsteel, aluminum, tungsten, composites, or any other types of materialthat can be reasonably adhered to the rear indentation 628 of the faceinsert 622 without departing from the scope and content of the presentinvention. The filler 630 material may have a have a second densitygreater than a density of the material used to create the face insert622 in one exemplary embodiment of the present invention; however, in analternative embodiment of the present invention, the filler 630 materialmay also have a second density that is less than the density of thematerial used to create the face insert 622 without departing from thescope and content of the present invention. In an alternativeembodiment, the frontal indentation 628 could be filled with a filler630 that is made out of a similar type material as the remainder of theface insert 622 to ensure sufficient bonding and cohesion between thematerials. More specifically, in this alternative embodiment, the filler630 material could be Ti-64, Ti-811, SP-700, ATI-425, or any other typeof titanium alloys all without departing from the scope and content ofthe present invention.

FIG. 6b shows a further alternative embodiment of the present inventionwherein the external surface of the face insert 622 could be coveredwith a cover layer 632 to ensure that the entire external surface of theface insert 622 has the same material to conform with the requirementsof the USGA. In one exemplary embodiment of the present invention thecover layer 632 may be made out of titanium type material similar to theremainder of the body; however, different types of titanium alloys couldbe used without departing from the scope and content of the presentinvention as long as it is capable of covering the external surface ofthe face insert 622.

In additional embodiments, the characteristics and methods illustratedand described herein can be applied to other portions of the golf clubhead which may include for example, the sole, the crown, etc. Each stepof the “stamped forging” process described above in reference to theface insert or the striking face can be applied to another portion ofthe golf club head which may include, for example, the sole, the crown,etc.

FIG. 7 of the accompanying drawings shows a perspective view of a golfclub head 1000 including a striking face 1100, a crown 1200, a sole1300, and a hosel 1400. The golf club head 1000 includes a forwardportion 1500 including the striking face 1100 and an aft portion 1600opposite the striking face 1100. FIG. 8 of the accompanying drawingsshows a front elevation view of the golf club head 1000 of FIG. 7. Thegolf club head 1000 includes a heel portion 1700 adjacent the hosel 1400and a toe portion 1800 opposite the heel portion 1700. In someembodiments, the golf club head 1000 can comprise a face insertconstruction. In additional embodiments, the golf club head 1000 cancomprise other constructions which may include for example, a C shapedface cup, an L shaped face cup, a T shaped face cup, or any othersuitable geometry all without departing from the scope and content ofthe present invention.

In some embodiments, various portions of the golf club head 1000 such asthe striking face 1100, crown 1200, and sole 1300 can be formedseparately and adjoined to form the golf club head 1000. It can beadvantageous to vary the thickness of the different portions to reduceweight, reduce stress, alter the performance of the golf club head 1000,and even to alter the acoustic characteristics of the golf club head1000. FIGS. 9-16 illustrate various embodiments and methods ofconstruction of the crown portion 1200 of a golf club head 1000. Inadditional embodiments, the characteristics and methods illustrated anddescribed herein can be applied to other portions of the golf club head1000 which may include for example, the sole 1300, the striking face1100, etc.

FIG. 9 of the accompanying drawings shows a top view of the externalsurface 1210 of one embodiment of a crown 1200. In some embodiments,including the one illustrated in FIG. 9, the external surface 1210 ofthe crown 1200 can be smooth to create a clean appearance when viewingthe golf club head from the address position. FIG. 9 of the accompanyingdrawings shows a cross-sectional line C-C′ dividing the crown 1200 toshow the relative thicknesses of the various regions in FIG. 11. Thiscross-sectional line C-C′ may also be known as a crown dividing line,spanning horizontally through the heel 1700 and toe portion 1800 of thecrown 1200 and providing a view from the forward portion 1500 lookingtoward the aft portion 1600 of the crown 1200. FIG. 10 of theaccompanying drawings shows a bottom view of the internal surface 1220of the crown 1200 of FIG. 9. FIG. 10 also shows a cross-sectional lineC-C′ dividing the crown 1200 to show the relative thicknesses of thevarious regions in FIG. 11

FIG. 11 of the accompanying drawings shows a cross-sectional view of thecrown 1200 taken across cross-sectional line C-C′ as shown in FIGS. 9and 10. In some embodiments the crown 1200 can include variablethickness. The crown 1200 can include at least one thick region 1240 andat least one thin region 1230. In some embodiments, as illustrated inFIGS. 10 and 11, the crown 1200 can include a plurality of thin regions1230 with a thickness D8 and a plurality of thick regions 1240 with athickness D9. The thicknesses D8 of the thin regions 1230 is measured atthe center of the thin regions 1230 and the thickness D9 of the thickregions 1240 is measured at the center of the thick regions 1240. Thethickness in the transition regions between the thick regions 1240 andthin regions 1230 can vary between the thickness D9 of the thick region1240 and the thickness D8 of the thin region 1230. In some embodiments,the transition regions between the thick regions 1240 and thin regions13230 can comprise a taper or a curve. In additional embodiments, thecrown 1200 can include additional regions with thicknesses differentthan the thin regions 1230 and thick regions 1240. In some embodiments,the thickness of the thin region 1230 can be thicker in the forwardportion 1500 and thinner in the aft portion 1600.

In some embodiments, the thickness D8 of the thin regions 1230 cangenerally be between 0.1 mm and 1.0 mm. In some embodiments, thethickness D8 of the thin regions 1230 can generally be between 0.2 mmand 0.5 mm. In some embodiments, the thickness D8 of the thin regions1230 can generally be between 0.3 mm and 0.4 mm. In some embodiments,the thickness D8 of the thin regions 1230 can generally be between 0.325mm and 0.375 mm. In some embodiments, the thickness D8 of the thinregions 1230 can generally be between 0.340 mm and 0.360 mm. In someembodiments, the thickness D9 of the thick regions 1240 can generally bebetween 0.1 mm and 1.0 mm. In some embodiments, the thickness D9 of thethick regions 1240 can generally be between 0.2 mm and 0.8 mm. In someembodiments, the thickness D9 of the thick regions 1240 can generally bebetween 0.3 mm and 0.7 mm. In some embodiments, the thickness D9 of thethick regions 1240 can generally be between 0.4 mm and 0.6 mm. In someembodiments, the thickness D9 of the thick regions 1240 can generally bebetween 0.45 mm and 0.55 mm. In some embodiments, the thickness D9 ofthe thick regions 1240 can generally be between 0.48 mm and 0.52 mm. Insome embodiments, the thickness D9 of the thick regions 1240 cangenerally be between 0.49 mm and 0.51 mm.

The geometry and orientation of the thick regions 1240 and thin regions1230 can include ribs 1250 extending away from the thin region 1230. Insome embodiments, the thick regions 1240 can comprise for example,forward aft ribs 1250 as illustrated in FIGS. 10 and 11. As illustratedin FIG. 11, the ribs 1250 can comprise a protrusion extending into theinterior of the golf club head 1000 from the internal surface 1220 ofthe crown 1200. The ribs 1250 can add structural support to the crown1200 and the thin regions 1230 can minimize the weight of the crown1200, providing a golf club manufacturer with the ability to placeweight elsewhere in the golf club head 1000 to maximize performance. Thethickness D9 of the thick region 1240 comprises both the thickness D8 ofthe thin region 1230 in addition to the distance the thick region 1240protrudes away from the inner surface 1220 of the thin region 1230. Insome embodiments, the plurality of thick regions 1240 may share the samethickness D9. In some embodiments, the plurality of thin regions 1230may share the same thickness D8.

In additional embodiments, the thickness of various thick regions 1240or thin regions 1230 may vary in order to optimize the performance ofthe golf club head 1000. In some embodiments, at least one of theplurality of thick regions 1240 can comprise a different thickness thananother thick region 1240. In some embodiments, at least one of theplurality of thin regions 1230 can comprise a different thickness thananother thin region 1230. In some embodiments, the thickness of at leastone thick region 1240 or thin region 1230 may vary along its length. Insome embodiments, at least one thick region 1240 can be thicker near theforward portion 1500 of the golf club head 1000 and thinner near the aftportion 1600 of the golf club head. In some embodiments, at least onethick region 1240 can be thicker near the forward portion 1500 and theaft portion 1600 of the golf club head of the golf club head 1000 andthinner in portion between the forward portion 1500 and aft portion1600. In some embodiments, at least one thin region 1230 can be thickernear the forward portion 1500 of the golf club head 1000 and thinnernear the aft portion 1600 of the golf club head. In some embodiments, atleast one thin region 1230 can be thicker near the forward portion 1500and the aft portion 1600 of the golf club head of the golf club head1000 and thinner in portion between the forward portion 1500 and aftportion 1600. In other embodiments, the thickness of the thick regions1240 and thin regions 1230 can vary from the heel side of the golf clubhead 1000 to the toe side.

In additional embodiments, the thick regions 1240 and thin regions 1230can include additional geometries and orientations, which may includefor example, the heel toe ribs 1250 as illustrated in FIG. 12 or thecriss-cross rib 1250 pattern as illustrated in FIG. 13. In additionalembodiments (not illustrated), thick regions 1240 can extend outwardfrom the external surface 1210 of the crown 1200. In additionalembodiments (not illustrated), the thick regions 1240 can both extendinward into the interior of the golf club head 1000 from the internalsurface 1220 of the crown 1200 and outwards from the external surface1210 of the crown 1200.

Machining the geometries described herein can be difficult and costprohibitive. In some embodiments, the geometries described herein can beconstructed utilizing an innovative process called “stamped forging”detailed in FIGS. 14A-C, 15A-C, 16A-B and described herein. During the“stamped forging” process the crown 1200 does not experience any phasetransformation, but is merely warmed to a malleable temperature to allowdeformation without the actual melting of the crown 1200.

FIG. 14A shows a cross sectional view of the first step of the stampedforging process wherein the crown 1200 is placed between a top punch2000 and a bottom cavity 3000 configured to deform the crown 1200. Thetop punch 2000 can comprise a plurality of protrusions 2100 arranged toreflect the pattern of thick regions 1240 in the crown 1200. The bottomcavity 3000 can comprise a corresponding plurality of depressions 3100which also reflects the pattern of thick regions 1240 in the crown 1200.Although not illustrated, in some embodiments, the top punch engagementsurface 2200 or the bottom cavity engagement surface 3200 can vary indepth to vary the thickness among the thin regions 1230 of the crown1200. In addition, in some embodiments, the depth of the protrusions2100 in the top punch 2000 and depressions 3100 in the bottom cavity3000 can vary to create a variable thickness among the plurality ofthick regions 1240 of the crown 1200.

FIG. 14B shows a cross sectional view of the next step of the stampedforging process wherein the top punch 2000 compresses towards the bottomcavity 3000 to alter the shape and geometry of the crown 1200. In someembodiments, the crown 1200 can be heated to about 830° C. for about 300seconds to increase the malleability of the crown 1200 to allow fordeformation. In some embodiments, the top punch 2000 generally appliesabout 100 MPa of pressure onto the crown 1200 for about 2 seconds tocreate the desired geometry. In other embodiments, the crown 1200 can beheated to about 1080° C. for about 300 seconds to increase themalleability of the crown 1200 to allow for deformation. In additionalembodiments, the crown can be heated to a temperature between about 700°C. and 1300° C. In another embodiment, the crown can be heated to atemperature between about 750° C. and 900° C. In another embodiment, thecrown can be heated to a temperature between about 800° C. and 850° C.In another embodiment, the crown can be heated to a temperature betweenabout 1000° C. and 1200° C. In another embodiment, the crown can beheated to a temperature between about 1050° C. and 1100° C.

FIG. 14C shows the next step of the stamped forging process wherein thetop punch 2000 is retracted away from the bottom cavity 3000 and off ofthe crown 1200. In some embodiments, the portion of the crown 1200facing the top punch 2000 will eventually become the external surface1210 of the crown 1200 while the portion of the crown 1200 facing thebottom cavity 3000 will eventually become be the internal surface 1220of the crown 1200. This process ensures that a precise geometry can beachieved on the internal surface 1220 of the crown 1200 without the needfor excessive machining. In other embodiments, not illustrated, theopposite may be true and the portion of the crown facing the top punch2000 will eventually become the internal surface 1220 of the crown 1200while the portion of the crown 1200 facing the bottom cavity 3000 willeventually become be the external surface 1210 of the crown 1200.

Although the steps described above in FIGS. 14A-14C may be sufficient tocreate the desired geometry in some circumstances, additional stepssimilar to the ones described above may be repeated to achieve moreprecise and complicated geometries. In the alternative embodimentswherein multiple stamped forging steps are required, the process couldbe repeated for rough and fine stamped forging without departing fromthe scope and content of the present invention. In fact, the stepsdescribed could be repeated three time, four times, or any number oftimes necessary to achieve the desired geometry all without departingfrom the scope and content of the present invention. In cases whereinmultiple stamped forging steps are needed, the shape and geometry of thetop punch 2000 and the bottom cavity 3000 may even be slightly differentfrom one another, with each finer mold having a closer resemblance tothe final finished geometry.

Once the geometry of the internal surface 1220 of the crown is formedvia the above prescribed methodology, the external surface 1210 of thecrown can be machined flat. Machining the external surface 1210 flat canbe more cost effective then machining the geometry into the internalsurface 1220 of the crown 1200. FIGS. 15A-15C illustrated the stepsinvolved in machining off the excess material of the crown 1200. FIGS.15A-15C show side views of a crown 1200 together with the bottom cavity3000 after the top punch (not shown) has created the desired geometry bydeforming the shape of the crown 1200 in the previous steps. Asillustrated in FIGS. 15A-15C, the excess material of the crown 1200 isremoved via a cutter 4000. The excess material, as shown in theembodiment illustrated in FIG. 15A, is generally defined as any materialthat is above the cutting line 4100. In some embodiments, the cuttingline 4100 can be located along a flat surface that significantly alignswith the bottom of the indentations 1260 formed in the crown 1200. Inmost embodiments, the cutting line 4100 can be offset slightly below thebottom of the indentations 1260 of the crown 1200 to allow for a precisefinish of the external surface 1210 of the crown 1200.

The position of the cutting line 4100 can be important, as it determinesthe thickness D8 of the thin region 1230. In order to more accuratelydefine the cutting line 4100, the distance D10 is identified in FIG.15A. The distance D10 signifies the distance between the bottom cavityengagement surface 3200 and the cutting line 4100. In some embodiments,the distance D10 mirrors the thickness D8 of the thin region 1230 of thecrown 1200. However, in some embodiments, the thin region 1230 of thecrown 1200 could have a variable thickness, making it difficult todetermine the thickness D8 of the crown 1200 and the height of thecutting line 4100 from the bottom cavity engagement surface 3200. Thedistance D10 may not be consistent across the cross section of the crown1200 if the bottom cavity engagement surface 3200 is not flat. In suchembodiments, the corresponding thickness D8 of the thin region 1230 mayvary across the crown 1200. Thus, a distance D11 is identified in FIG.15A, which represents the distance from the bottom of the depressions3100 of the bottom cavity to the cutting line 4100. In some embodiments,the distance D11 mirrors the thickness D9 of the thick region 1240 ofthe crown 1200.

The cutter 4000 may generally be a fly cutter type cutter to ensure asmooth surface that will eventually form the external surface 1210 ofthe crown 1200, however, numerous other types of cutters 4000 may beused without departing from the scope and content of the presentinvention. More specifically, alternative cutters 4000 may include anend mill clutter, a ball nose cutter, a side cutter, face cutter, awoodruff cutter, a shell mill cutter, or any type of milling cutter allwithout departing from the scope and content of the present invention.In fact, the finished surface could even potentially be achieved by anyalternative finishing techniques, which may include, for example,polishing, that could create a flat surface all without departing fromthe scope and content of the present invention.

FIG. 15B shows an intermediary stage of the cutting process wherein thecutter 4000 begins to remove excess material from the crown 1200 alongcutting line 4100. Finally, FIG. 15C shows the crown 1200 in accordancewith an exemplary embodiment of the present invention wherein the excessmaterial has been removed by the cutter 4000. The crown 1200 can then bebent as illustrated in FIGS. 16A and 16B to the required curvature. Thecrown 1200 can be removed from the bottom cavity 3000 and positionedbetween an external die 5000 and an internal die 6000 as illustrated inFIG. 16A. The external die 5000 can comprise a concave engagementsurface 5100 configured to engage the external surface 1210 of the crown1200. The internal die 6000 can comprise a convex engagement surface6100 configured to engage the internal surface 1220 of the crown 1200.The external die 5000 can be forced towards the internal die 6000,curving the crown 1200 to the desired geometry as illustrated in FIG.16B. In some embodiments, not illustrated, the internal die 6000 cancomprise depressions similar to the bottom cavity 3000 described earlierto receive the ribs 1250 of the crown 1200. As it can be seen fromabove, the innovative forming and finishing method is a majorimprovement in simplifying the machining process involved to a simpleone pass finish, especially when compared to the alternatives ofmachining the actual variable thickness geometry or masking off thegeometry and utilizing chemical etching techniques.

In another embodiment, the steps of the stamped forging processdescribed in reference to FIGS. 14A-14C and 16A-16C can be completedsimultaneously. FIG. 17A shows a cross sectional view of a deformedcrown 1200 between a curved top punch 7000 and a curved bottom cavity8000. The top punch 7000 can be curved, much like the curved externaldie 5000 illustrated in FIGS. 16A-B, and the engagement surface 7200comprise a plurality of protrusions 7100 arranged to reflect the patternof thick regions 1240 in the crown 1200. The bottom cavity 8000 can becurved, much like the curved internal die 6000 illustrated in FIGS.16A-B, and the engagement surface 8200 can comprise a correspondingplurality of depressions 8100 which also reflect the pattern of thickregions 1240 in the crown 1200. After the crown is deformed by thecurved top punch 7000 and curved bottom cavity 8000, excess material canbe machined off the crown. FIG. 17B shows a cross sectional view of thecrown 1200 being machined by the cutter 4000. FIG. 17C shows a crosssectional view of the crown 1200 after being machined by the cutter4000. In some embodiments, as illustrated in FIG. 17B, the crown 1200can remain positioned on the curved bottom cavity 8000 during themachining. In some embodiments, rather than machining a flat surface asdescribed in relation to FIGS. 15A-15C, the cutter 4000 will machineexcess material off the crown 1200 to create a curved external surface1210, as illustrated in FIGS. 17B and 17C, while leaving the ribs 1250on the internal surface 1220 of the crown.

In additional embodiments, the characteristics and methods illustratedand described herein can be applied to other portions of the golf clubhead which may include for example, the sole, the striking face, etc.Each step of the “stamped forging” process described above in referenceto the crown or the striking face can be applied to another portion ofthe golf club head which may include, for example, the sole, thestriking face, the crown, etc. The “stamped forging” methods describedherein are particularly useful for imparting a variable thicknessgeometry to a portion of a golf club head, particularly one in which theexternal surface is desired to have a smooth surface and the insidesurface desirably includes thick regions of a particular geometry toalter the performance characteristics of the golf club head. Additionalthickness variations and geometries of various portions of the golf clubhead are possible utilizing the methods described herein. For example,the process could be modified such that the variable thickness geometryis exposed on the exterior surface of the golf club head rather than theinterior as illustrated and described herein. In addition, the methodsdescribed herein can be applied to irons and putters in addition themetal wood clubs illustrated in the Figures. The face of an iron typegolf club, for example, could be formed utilizing the stamped forgingmethods described herein and then welded or bonded to the body of thegolf club head.

FIG. 18 illustrates a perspective view of a golf club head 1000including a striking face 1100, a crown 1200, a sole 1300, and a hosel1400. The striking face and crowns described earlier were created usinga stamped forging process. In some embodiments, it can be advantageousand more cost effective to create portions of the golf club head 1000via casting. For illustrative purposes, we will assume the golf clubhead 1000 is a face-pull cast construction, which means the body portion1610, the majority of the golf club head 1000, is cast and the castingtooling is pulled through a window in the striking face 1100 of the golfclub head 1000. Once the body portion 1610 of the golf club head 1000 iscast then a face insert 1110 is welded to the golf club head 1000,filling the window. Other castable constructions are possible andcompatible with the construction techniques described herein. Most golfclub heads are cast via investment casting techniques, but other castingmethods can be used such as sand casting, die casting, etc.

Casting does have its limitations, one of which being the minimum wallthicknesses required. During casting, the molten metal needs to flowthrough the various portions of the golf club head and that flow can beinhibited by very thin portions. Casting thinner than a minimum castablethickness can lead to voids and porosity in the casting which decreasethe strength and increase stress risers in the golf club head.Therefore, it can be impossible to cast some of the geometries describedherein if the thin regions are thinner than the minimum castablethickness. One desirable geometry that is difficult to achieve withexisting casting methods, is a crown incorporating at least one thinregion that is thinner than the minimum castable thickness, one exampleof which is illustrated in FIGS. 19 and 20. FIG. 19 illustrates aperspective view of the golf club head 1000 of FIG. 18, including a thinregion 1230 located in the crown 1200. FIG. 20 illustrates across-sectional view of the crown 1200 of FIG. 19. The crown 1200 of thegolf club head 1000 includes a variable thickness geometry. The crown1200 includes an external surface 1210 and an internal surface 1220. Theinternal surface 1220 is adjacent the hollow interior of the golf clubhead 1000 and the external surface 1210 is opposite the internal surface1220. The external surface is substantially smooth. The internal surfaceincludes a recess 1270, causing the crown 1200 to have a thin region1230 and a thick region 1240. The thin region has a thickness T_(thin)which is less than the minimum castable thickness. The thick region hasa thickness T_(thick) which is thicker than the thickness T_(thin). Therecess has a depth D_(r).

The minimum castable thickness to create repeatable quality castings istypically greater than or equal to 0.52 mm. Recent developments incasting techniques have had success casting as thin as 0.48 mm. The“minimum castable thickness” will be defined as 0.48 mm herein unlessnoted otherwise. Typically, the thick region will have a thicknessgreater than or equal to the minimum castable thickness. The thicknessof the thin region T_(thin) is preferably less than or equal to 0.45 mm.In an additional embodiment, the thickness of the thin region T_(thin)is preferably less than or equal to 0.35 mm. In an additionalembodiment, the thickness of the thin region T_(thin) is preferably lessthan or equal to 0.25 mm. The depth of the recess D_(r) can be greaterthan or equal to 0.05 mm and less than or equal to 0.35 mm. In anadditional embodiment, the depth of the recess D_(r) can be greater thanor equal to 0.15 mm and less than or equal to 0.25 mm. In an additionalembodiment, the depth of the recess D_(r) can be approximately 0.20 mm.

One way to overcome the casting limitations described above, is a newand creative method of creating variable thickness geometries in golfclub heads, which is illustrated in FIGS. 21 and 22. This method can beapplied to a crown, as described herein, or it can be applied to otherportions of a golf club head, which may include for example, thestriking face, the sole, etc. The method is particularly applicable to aface-pull cast construction as described above wherein the body portionis cast. The method incorporates specific casting geometries andchemical etching, which can also be referred to as chemical milling orindustrial etching. Chemical etching uses etching chemicals to removematerial from a golf club head. The material to be removed is normallyput in a bath of the etching chemical, a corrosive chemical, sometimescalled an etchant, which reacts with the material and causes thematerial to be dissolved. The amount of material dissolved generallydepends on how long the material is exposed to the etching chemical.

Masking can be utilized to prevent the etching chemical from removingmaterial from particular portions of the golf club head. Masking layersare generally formed of inert substances and can be applied to the golfclub head in a variety of ways, which may include, for example, dipping,painting, flow coating, electrostatic deposition, adhesive sheet, etc.After the chemical etching is complete, the masking layer can beremoved.

The casting and etching method is illustrated in FIGS. 21A-21D andoutlined in FIG. 22. First 10001, the body portion of the golf club headis cast. In this embodiment, the desired variable thickness geometry islocated in the crown 1200 of the golf club head. FIG. 21A illustrates across-sectional view of a crown 1200 after casting. Like the finishedcrown in FIG. 20, the crown 1200 in FIG. 21A includes a recess on theinternal surface 1220. Unlike the finished crown 1200 in FIG. 20, thecrown 1200 in FIG. 21A includes a sacrificial protrusion 1280 on theexternal surface of the crown 1200. The crown 1200 includes a firstregion 1201 and a second region 1202. The first region 1201 is where thefinal product will include a thin region 1230. The first region 1201includes the protrusion 1280 and the recess 1270. The second region isadjacent the protrusion 1280 and recess 1270. In some embodiments, thesecond region 1202 substantially surrounds the first region 1201. Theprotrusion 1280 extends outwards beyond the external surface of thesecond region 1202. The second region 1202 has a thickness T₂. The firstregion 1201 has a thickness T₁. Thickness T₂ is equal to or greater thanthe minimum castable thickness in order to facilitate quality andconsistent casting results. In some embodiments, thickness T₁ issubstantially similar to thickness T₂. The face insert 1110, or anyother portion of the golf club head 1000, can be welded to the bodyportion 1610 at this time as well.

Next 10002, a mask 9000 is applied to the external surface 1210 of thesecond region 1202 of the crown 1200, as illustrated in FIG. 21B. A maskis not applied to the external surface 1210 of the first region 1201.Masking can be applied the entire casting minus the first region 1201.Additionally, any holes from the hollow golf club head interior to theexterior of the golf club head can be plugged, preventing the etchingmaterial from entering the hollow interior of the golf club head.

Next 10003, the crown 1200 is exposed to an etching chemical, asillustrated in FIG. 21C. The etching chemical removes material from thefirst region 1201, removing the sacrificial protrusion 1280, until theexternal surface 1210 of the first region 1201 is substantially flushwith the external surface 1201 of the second portion. In anotherembodiment, the etching chemical removes material from the first region1201, until the thickness T₁ is less than the minimum castablethickness, or until it reaches T_(thin). After a specified amount oftime 10004, the etching chemical is removed from the golf club head. Inone embodiment, the entire club head is dipped into the etchingchemical. In another embodiment, a specific portion of the club head canbe lowered into an etching chemical, such as the crown, only partiallysubmerging the golf club head.

Finally 10005, the mask 9000 is removed from the second region 1202 ofthe crown 1200. The end product is a crown 1200, as illustrated in FIG.21D, where the external surface 1210 of the first region 1201 issubstantially flush with the external surface 1210 of the second region1202. The chemical etching has reduced the thickness of the first region1201 by removing the sacrificial protrusion, creating a thin region 1230adjacent the thick region 1240. Some embodiments include an additionalstep 10006 of polishing the external surface 1210 of the golf club head100 to ensure the external surface 1210 is smooth and the externalsurface 1210 of the first region 1201 is substantially flush with theexternal surface 1210 of the second region 1202.

The casting and chemical etching method described herein can be used tocreate a variety of variable thickness geometries, including but notlimited to those described herein relative to the chemical etchingmethod as well as the stamped forging process.

Other than in the operating example, or unless otherwise expresslyspecified, all of the numerical ranges, amounts, values and percentagessuch as those for amounts of materials, moment of inertias, center ofgravity locations, loft, draft angles, various performance ratios, andothers in the aforementioned portions of the specification may be readas if prefaced by the word “about” even though the term “about” may notexpressly appear in the value, amount, or range. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in theabove specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

It should be understood, of course, that the foregoing relates toexemplary embodiments of the present invention and that modificationsmay be made without departing from the spirit and scope of the inventionas set forth in the following claims.

What is claimed is:
 1. A method of forming a crown of a golf club head, comprising: casting said crown of said golf club head, said crown of said golf club head comprising an internal surface adjacent a hollow interior of said golf club head, and an external surface opposite said internal surface, said crown of said golf club head comprising a first region and a second region adjacent said first region, said second region substantially surrounding said first region, said first region comprising a recess formed in said internal surface, said first region comprising a sacrificial protrusion on said external surface extending outwards beyond said second region, wherein said first region of has an as-cast thickness T₁, and thickness T₁ is greater than or equal to 0.48 mm; applying a mask to said external surface of said second region; exposing said crown of said golf club head to an etching chemical, wherein said etching chemical removes said sacrificial protrusion from said external surface of said crown; removing said etching chemical from said crown of said golf club head; and removing said mask from said second region.
 2. A method of forming a portion of a golf club head, comprising: casting said portion of said golf club head, said portion of said golf club head comprising an internal surface adjacent a hollow interior of said golf club head, and an external surface opposite said internal surface, said portion of said golf club head comprising a first region and a second region adjacent said first region, said first region comprising a recess formed in said internal surface, said first region comprising a sacrificial protrusion on said external surface extending outwards beyond said second region; applying a mask to said external surface of said second region; exposing said portion of said golf club head to an etching chemical; removing said etching chemical from said portion of said golf club head; and removing said mask from said second region.
 3. The method of claim 2, further comprising polishing said external surface of said portion of said golf club head.
 4. The method of claim 2, wherein said first region of has an as-cast thickness T₁, and thickness T₁ is greater than or equal to 0.48 mm.
 5. The method of claim 4, wherein said thickness T₁ of said first region, after exposing said portion of said golf club head to an etching chemical, is reduced to less than or equal to 0.45 mm.
 6. The method of claim 4, wherein said thickness T₁ of said first region, after exposing said portion of said golf club head to an etching chemical, is reduced to less than or equal to 0.35 mm.
 7. The method of claim 4, wherein said thickness T₁ of said first region, after exposing said portion of said golf club head to an etching chemical, is reduced to less than or equal to 0.25 mm.
 8. The method of claim 2, wherein exposing said portion of said golf club head to an etching chemical removes said sacrificial protrusion from said first region.
 9. The method of claim 2, wherein exposing said portion of said golf club head to an etching chemical is completed when said external surface is substantially flush at the intersection of said first region and said second region.
 10. The method of claim 2, wherein said second region substantially surrounds said first region.
 11. The method of claim 2, wherein said second region has a thickness T₂, and wherein said recess has a depth D_(r), and wherein D_(r) is greater than or equal to T₂/2.
 12. A method of forming a crown of a golf club head, comprising: casting said crown of said golf club head, said crown of said golf club head comprising an internal surface adjacent a hollow interior of said golf club head, and an external surface opposite said internal surface, said crown of said golf club head comprising a first region and a second region adjacent said first region, said first region comprising a recess formed in said internal surface, said first region comprising a sacrificial protrusion on said external surface extending outwards beyond said second region; applying a mask to said external surface of said second region; exposing said crown of said golf club head to an etching chemical, wherein said etching chemical removes said sacrificial protrusion from said external surface of said crown; removing said etching chemical from said crown of said golf club head; and removing said mask from said second region.
 13. The method of claim 12, further comprising polishing said external surface of said crown of said golf club head.
 14. The method of claim 12, wherein said first region of has an as-cast thickness T₁, and thickness T₁ is greater than or equal to 0.48 mm.
 15. The method of claim 14, wherein said thickness T₁ of said first region, after exposing said crown of said golf club head to an etching chemical, is reduced to less than or equal to 0.45 mm.
 16. The method of claim 14, wherein said thickness T₁ of said first region after exposing said crown of said golf club head to an etching chemical is reduced to less than or equal to 0.35 mm.
 17. The method of claim 14, wherein said thickness T₁ of said first region after exposing said crown of said golf club head to an etching chemical is reduced to less than or equal to 0.25 mm.
 18. The method of claim 12, wherein exposing said crown of said golf club head to an etching chemical is completed when said external surface is substantially flush at the intersection of said first region and said second region.
 19. The method of claim 12, wherein said second region substantially surrounds said first region.
 20. The method of claim 12, wherein said second region has a thickness T₂, and wherein said recess has a depth D_(r), and wherein D_(r) is greater than or equal to T₂/2. 